Diesel engines are ubiquitous throughout the world. Valued for their power, performance, fuel economy, and durability, diesel trucks, buses, pumps and generators are more common than spark ignition engines. However, concerns over diesel exhaust, increasingly strict emissions regulations and rising fuel costs are forcing operators and fleet owners to seek cleaner alternatives.
Natural gas is one answer. Readily available in most parts of the world, it is generally cleaner than diesel and, due to local sources, natural gas is significantly cheaper than diesel in many parts of the world.
With the availability of inexpensive natural gas, many fleet owners, and other operators want to retrofit their diesel engines to burn natural gas. The problem is finding a way to cheaply do so. In addition, some owners of gasoline engines are interested in taking advantage of the lower costs of natural gas.
Conventional 100% conversion technologies, where a diesel engine is converted to burn, or combust 100% natural gas, require substantial modifications to the engine as the compression ratio has to be reduced and an ignition system must be installed. This takes time, is costly, and requires expensive special tooling.
Alternatively, diesel engines can be converted to operate in a “dual-fuel” or “multi-fuel” mode. In this conversion, a small amount of diesel is injected into the combustion cylinder, sometimes known as “pilot-injection,” which ignites, or combusts the alternative fuel (natural gas, propane or hydrogen) which was introduced into the intake manifold, and drawn into the combustion chamber. In this way, a percentage of the diesel can be replaced by the substitute gas resulting in lower exhaust emissions, especially particulate matter (PM). In addition, fuel costs are reduced, because natural gas is cheaper than diesel.
This multi-fuel operation does not require the substantial engine modifications of a 100% conversion. The multi-fuel conversions are performed so that the engine can be re-converted to operate on 100% diesel very easily, thus, the diesel fuel injectors are not replaced. However, the percentage of alternative fuel varies between idle, part throttle and full load or throttle. At idle the engine runs almost 100% on diesel because the amount of diesel being injected by the original injectors cannot be reduced further. At part throttle up to about 90% of the alternative fuel is used, but to protect the engine from destruction and overheating at full load, the percentage of the alternative fuel usually varies from 20% to 80%.
The amount of alternative fuel, such as natural gas, propane or hydrogen that is combusted must be carefully monitored, as the original diesel engine is not designed for the higher combustion temperatures generated by the alternative fuel. In addition, to maximize the cost savings associated with alternative fuel use, operators should be informed as to how much alternative fuel is being combusted.
Therefore, a need exists for an inexpensive diesel or gasoline engine conversion method and apparatus that informs the operator of the amount of alternative fuel that is being combusted.